February 22, 2015

Murphy and Mitchell (1974: fig. 1)

One thing that I’ve never understood is why some people are skeptical about sauropods using their tails defensively, when lizards do this all the time. I’ve been digging through the literature on this for a current project, and there are some really great accounts out there, and by ‘great’ I mean ‘scary’.

Here’s a key passage from Murphy and Mitchell (1974: p. 95):

V. salvator uses the tail to strike repeatedly in combination with biting for defense…Captive Varanus (varius, spenceri, mertensi, and salvadorii) use the tail for defense, but only salvadorii appears to aim directly for a handler’s eye. An adult male V. salvadorii accurately struck the senior author’s eye with the tip of the tail as he was attempting to maneuver the lizard. On many subsequent occasions, the monitor tried to strike the eye of the handler with accuracy.

Not being a monitor expert, I was initially thrown by the V. salvator/V. salvadorii issue. V. salvator is the water monitor, V. salvadorii is the crocodile monitor. Both get pretty darned big; Wikipedia lists 3.21 m (10.5 ft) for V. salvator and 2.44-3.23 m (8.0-10.6 ft) for V. salvadorii.

Anyway, I’d heard of lots of anecdotal reports of lizards from many clades using their tails to lash at rivals, predators, or handlers, but I’d never read about a lizard aiming directly for the target’s eyes. It immediately made me think about (1) sauropod tails, especially the whip-lash tails of flagellicaudan diplodocoids and at least some titanosaurs (Wilson et al. 1999), and (2) the supraorbital crests and ridges in many theropods, especially big Morrison forms like Allosaurus and Ceratosaurus. Of course, supraorbital crests in theropods could serve many functions, including shading the eyes and social and sexual display, but it’s interesting to speculate that they might have had a defensive function as well. Has anyone ever proposed that in print?

Diplodocus longus USNM 10865, from Gilmore (1932: plate 6)

Most of the papers that pooh-pooh the use of whiplash tails in defense (e.g., Myhrvold and Currie 1997) argue that the tail-tip would be too small to do any serious damage to a multi-ton attacker, and too fragile to survive an impact. This seems wrong-headed to me, like arguing that unless you find putative animal weapons broken and caked in their adversaries’ blood, they aren’t used as weapons. A structure doesn’t have to do lethal damage or any damage at all to serve as a weapon, as long as it dissuades a predator from attacking. I’d think that getting hit in the eye by a 35-foot bullwhip might convince an allosaur to go have a look at Camptosaurus instead.

Now, one could argue that if the whip-lash doesn’t do any serious damage, predators will learn to blow them off as dishonest signals (we’re assuming here that having your eye possibly knocked out doesn’t count as ‘serious damage’ to an allosaur). But it’s not like the whiplash was the only weapon a diplodocid could bring to bear: the proximal tail could probably deliver a respectable clobberin’, and then there’s the zero fun of being stomped on by an adversary massing a dozen tons or more. In that sense, the whip-lash is writing checks the rest of the body can certainly cash. It’s saying, “Getting hit with this will be no fun, and if that isn’t enough, there’s plenty more coming.”

All of this is leaving aside more obvious defensive adaptations of the tail in Shunosaurus, maybe Omeisaurus and Mamenchisaurus, and probably Spinophorosaurus (although I’d feel better about Spinophorosaurus if the association of the spikes and the tail was more secure). I suspect that all sauropod tails were useful in defense, but only some sauropod taxa used that behavior enough for a morphological enhancement (club, spikes, whiplash) to have evolved. Similarly, common snapping turtles, Chelydra serpentina, will wiggle their unspecialized tongues to attract fish (I’ve witnessed this myself in captive specimens) but lack the worm-shaped tongue lure found in the more ambush-specialized alligator snappers, Macrochelys temminckii. On reflection, there are probably few morphological changes in evolution that aren’t preceded by behavior. Not in a Lamarckian sense, just that certain variations aren’t useful unless the organism is already (suboptimally) performing the relevant function.

Bonus observation: Mike noted back when that Shunosaurus and Varanus retain complex caudal vertebrae all the way out to the end. Since in this case ‘complex’ means ‘having processes that muscles can attach to’, maybe that has something to do with keeping up relatively fine motor control in your bad-guy-whomping organ. Would be interesting to compare caudal morphology between tail-whomping lizards and committed caudal pacifists (assuming we can find any of the latter that we’re certain about – maybe tail-whomping just doesn’t get used very often in some taxa, like those that have caudal autotomy). Anyone know anything about that?

In the top 24 images, I see that half of them are of the building itself — rightly so, as it’s a beautiful and impressive piece of architecture that would be well worth visiting even if it was empty. Of the rest, ten are of specimens inside the museum: and every single one of them is of the Diplodocus in the main hall. (The other two photos are from the French natural history museum, so don’t really belong in this set. Not coincidentally, they are both primarily photos of the French cast of the same Diplodocus.)

The NHM’s Diplodocus — I can’t bring myself to call it “Dippy” is the icon of the museum. It’s what kids go to see. It’s what the museum used as the basis of the logo for the 2005 SVPCA meeting that was held there. It’s essentially the museum mascot — the thing that everyone thinks of when they think of the NHM.

And rightly so: it’s not just a beautiful specimen, it’s not just sensational for the kids. As the first cast ever made of the Carnegie specimen CM 84, it’s a historically important object in its own right. It was the first mounted Diplodocus ever, being presented in 1905 before the the original material was even on display in Pittsburgh.

Or, no — wait — it does already have a blue whale hall. That’s it. That’s what I meant to say. And very impressive it is, too.

I don’t mind admitting that the whale hall is my second favourite room in the museum. Whenever I go there as a tourist (rather than as a scientist, when I spend all my time in the basement), I make sure I see it. It’s great.

The thing is, it’s already there. A museum with a whale hall does not need another whale hall.

One of the more breathtaking parts of this planned substitution is the idea that Diplodocus is no longer relevant. The NHM’s director, Sir Michael Dixon says the change is “about asking real questions of contemporary relevance”. He says “going forward we want to tell more of these stories about the societally relevant research that we do”. This “relevance” rhetoric is everywhere. The museum “must move with the times to stay relevant”, writes Henry Nicholls in the Guardian.

There was a time when Diplodocus was relevant, you know: waaay back in the 1970s. But time has moved on, and now that’s 150,000,035 years old, it’s become outdated.

Conversely, the rationale for the whale seems to be that they want to use it as a warning about extinction. But could there ever be a more powerful icon of extinction than a dinosaur?

The thing is, the right solution is so obvious. Here’s what they want to do:

Clearly the solution is, yes, hang the whale from the ceiling — but don’t remove the Diplodocus. Because, seriously, what could be a better warning about extinction than the juxtaposition of a glorious animal that we lost with one that we could be about to lose?

All this argument about which is better, a Diplodocus or a blue whale: what a waste of energy. Why should we have to choose? Let’s have both.

I’ve even had an artist’s impression made, at great expense, to show how the combination exhibit would look. Check it out.

(If anyone would like to attempt an even better rendering, please by my guest. Let me know, and I’ll add artwork to this page.)

February 2, 2015

Introduction and Background

An epipophysis in a neural arch of a juvenile Apatosaurus, CM 555. From this post.

I have three goals with this post:

To document the range of variation in epipophyses in the cervical vertebrae of sauropods.

To show that the “finger-like processes” overhanging the cervical postzygapophyses in the newly described Qijianglong are not novel or mysterious structures, just very well developed epipophyses.

Finally, to show that similar long, overhanging epipophyses are present in other mamenchisaurids, although as far as I can tell no-one has noted them previously.

Epipophyses are muscle attachment points dorsal to the postzygapophyses, for the insertion of long, multi-segment epaxial (dorsal) neck muscles in birds and other dinosaurs. I know that they turn up occasionally in non-dinosaurian archosaurs, and possibly in other amniotes, but for the purposes of this post I’m only considering their distribution in sauropods. For some quick background info on epipophyses and the muscles that attach to them, see the second half of this post, and see Wedel and Sanders (2002) and Taylor and Wedel (2013a) for further discussion and more pictures.

Before we start with the pictures, a fiddly nomenclatural point: this muscle attachment point dorsal to the postzyg has traded under at least six names to date.

The ‘Owenian’ term, used by virtually all non-avian theropod workers, by Sereno et al. (1999) for Jobaria, and probably by loads of other sauropod workers (including myself, lately) is epipophysis.

Beddard (1898) referred to this feature in birds as the hyperapophysis; this term seems to have fallen completely out of use.

Boas (1929), again referring to birds, called it the processus dorsalis. Zweers et al. (1987: page 138 and table 1) followed this terminology, which is how I learned of it when I was an undergrad at OU.

Baumel and Witmer (1993) called this feature in birds the torus dorsalis (note 125 on page 87), which some authors have informalized to dorsal torus (e.g., Harris 2004: page 1243 and fig. 1). Baumel and Witmer (1993: page 87) note that, “the use of ‘Torus’ is preferable since it avoids confusion with the spinous [dorsal] process of the neural arch”.

In my own early papers (e.g., Wedel et al. 2000b) and blog posts I called this feature the dorsal tubercle, which was my own attempt at an informal term matching ‘processus dorsalis’ or ‘torus dorsalis’. That was unfortunate, since there are already several other anatomical features in vertebrates that go by the same name, including the dorsal-facing bump on the dorsal arch of the atlas in many vertebrates, and a bump on the humerus in birds and some other taxa. In more recent papers (e.g., Taylor and Wedel 2013a) I’ve switched over to ‘epipophysis’.

In the last post, Mike coined the term parapostzygapophysis for this feature in Qijianglong. [Note: he now regrets this.]

As usual, if you know of more terms for this feature, or additional history on the ones listed above, please let us know in the comments.

Now, on to the survey.

Prosauropods

I haven’t seen very many prominent epipophyses in basal sauropodomorphs. Probably the best are these in the near-sauropod Leonerasaurus, which is very sauropod-like in other ways as well. Modifed from Pol et al. (2011: fig. 5).

This combination of photograph and interpretive drawing neatly shows why it’s often difficult to spot epipophyses in photos: unless you can make out the postzygapophyseal facet, which is often located more anteriorly than you might guess, you can’t tell when the epipophysis projects further posteriorly, as in the last of these vertebrae. In this case you can make it out, but only because the interpretive drawing shows the facet much more clearly than the photo.

Basal sauropods

The most basal sauropod in which I have seen clear evidence of epipophyses is Tazoudasaurus. They’re not very apparent in lateral view, but in posterior view the epipophyses are clearly visible as bumps in the spinopostzygapophyeal laminae (SPOLs). Modified from Allain and Aquesbi (2008: fig. 9).

In addition to Qijianglong, some other basal eusauropods have prominent epipophyses. Probably the best known is Jobaria; Sereno et al. (1999: fig. 3) figured and labeled the epipophysis in one of the cervical vertebrae. The vertebra image in that figure is tiny (nice work, glam-magz!), so here are some sketches of Jobaria mid-cervicals (from two different individuals) that I made back in the day when I was doing the research for Gary Staab’s Jobaria neck sculpture (see Sanders et al. 2000 for our SVP abstract about that project).

Turiasaurus also has prominent, overhanging epipophyses in at least some of its cervical vertebrae. You can just make one out as a tiny spike a few pixels long in Royo-Torres et al. (2006: fig. 1K). I have seen that cervical firsthand and I can confirm that the epipophyses in Turiasaurus are virtually identical to those in Jobaria.

Other mamenchisaurids

It’s not air-tight, but there is suggestive evidence of projecting epipophyses in some other mamenchisaurids besides Qijianglong.

If you’re really hardcore, you may remember that back in 2005, Mike got to go up on a lift at the Field Museum of Natural History to get acquainted with a cast skeleton of Mamenchisaurus hochuanensis that was mounted there temporarily. During that adventure he took some photos that seem to show projecting epipophyses in at least two of the mid-cervicals. At least, if they’re not epipophyses, I don’t know what they might be.

Here they are again in medial view. My only reservation is that these vertebrae were distorted to begin with, and some features of the cast are very difficult to interpret. So, probably epipophyses, but it would be nice to check the original material at some point.

Something similar may be present in some posterior cervical vertebrae of Mamenchisaurus youngi. Here’s Figure 17 from Ouyang and Ye (2002). The “poz” label does not not seem to be pointing to the articular facet of the postzygapophysis, which looks to be a little more anterior and ventral, below the margin of the PODL. If that’s the case, then C15 has long, overhanging epipophyses like those of Jobaria. C16 has a more conservative bump, which is to be expected – the epipophyses typically disappear through the cervico-dorsal transition.

Finally, here’s a cervical vertebra of Omeisaurus junghsiensis from Young (1939: fig. 2). I don’t want to hang very much on just a few pixels, but my best guess at the extent of the postzygapophyseal articular facet is shown in the interpretation above. If that’s correct, then this specimen of Omeisaurus had really long epipophyses, rivaling those of Qijianglong. Unfortunately that’s impossible to check, because this specimen has been lost (pers. comm. from Dave Hone, cited in Taylor and Wedel 2013).

Diplodocoidea

Haplocanthosaurus nicely shows that the epipophyses can be large in terms of potential muscle attachment area without projecting beyond the posterior margins of the postzygapophyses. Here is C14 of H. priscus, CM 572, in posterior and lateral views, modified from Hatcher (1903: plate 1).

Of course, the champion epiphysis-bearer among diplodocoids is the weird little rebbachisaurid Nigersaurus. Here’s a Nigersaurus mid-cervical, from Sereno et al. (2007: fig. 3). Note that the projecting portions of the epipophysis is roughly as long as the articular surface of the postzygapophysis.

Macronaria

The epipophysis in this cervical of Australodocus just barely projects beyond the posterior margin of the postzygapophysis.

In Giraffatitan, epipophyses are absent or small in anterior cervicals but they are prominent in C6-C8. Here’s a posterolateral view of C8, showing very large epipophyses that are elevated several centimeters above the postzygapophyses. You can also see clearly in this view that the spinopostzygapophyseal lamina (SPOL) and postzygodiapophyseal lamina (PODL) converge at the epipophysis, not the postzygapophysis itself.

The holotype of Sauroposeidon, OMNH 53062, is similar to Giraffatitan in that the two anterior cervical vertebrae (possibly C5 and C6) have no visible epipophyses, but epipophyses are prominent in the two more posterior vertebrae (possibly C7 and C8). Click to enlarge – I traced the articular facet of the postzygapophysis in ?C8 to more clearly separate it from the epipophysis. For a high resolution photograph of that same vertebra that clearly shows the postzyg facet and the epipophysis dorsal to it, see this post.

Oddly enough, I’ve never seen prominent epipophyses in a titanosaur. In Malawisaurus, Trigonosaurus, Futalognkosaurus, Rapetosaurus, Alamosaurus, and Saltasaurus, the SPOLs (such as they are – inflated-looking titanosaur cervicals do not have the same crisply-defined laminae seen in most other sauropods) merge into the postzygapophyseal rami and there are no bumps sticking up above or out beyond the articular facets of the postzygs. I don’t know what to make of that, except to note that several of the animals just mentioned have mediolaterally wide, almost balloon-shaped cervical neural spines. In our 2013 PeerJ paper, Mike and I argued that the combination of tall neural spines and tall epipophyses in the cervical vertebrae of sauropods made them functionally intermediate between crocs (huge neural spines, no epipophyses) and birds (small or nearly nonexistent neural spines, big epipophyses). Perhaps most titanosaurs reverted to a more croc-like arrangement with most of the long epaxial neck muscles inserting on the neural spine instead of the postzygapophyseal ramus. I’ve never seen that possibility discussed anywhere, nor the apparent absence of epipophyses in most titanosaurs. As usual, if you know otherwise, please let me know in the comments!

Cervical vertebrae of Malawisaurus from Gomani (2005: fig. 9): not an epipophysis in sight. But check out the spike-like neural spines – these are so wide from side to side that from the front they look like party balloons.

And as long as we’re discussing the phylogenetic distribution of epipophyses, it is interesting that long, overhanging epipophyses are so broadly but sporadically distributed. They turn up in some non-neosauropods (Jobaria, Turiasaurus, Omeisaurus) and some diplodocoids (Nigersaurus, the occasional vertebra in Diplodocus and Leinkupal), but not in all members of either assemblage, and they seem to be absent in Macronaria (although many non-titanosaurs have shorter epipophyses that don’t overhang the postzygs). I strongly suspect that a lot of this is actually individual variation that we’re not perceiving as such because our sample sizes of almost all sauropods are tiny, usually just one individual. Epipophyses are definitely muscle attachment sites in birds and no better hypothesis has been advanced to explain their presence in other archosaurs. Muscle attachment scars are notoriously variable in terms of their relative development and expression among individuals, and it would be odd if epipophyses were somehow exempt from that inherent variability.

It also seems more than likely that ontogeny plays a role: progressive ossification of tendons attached at the epipophyses would have the effect of elongating the preserved projection. And since for some aspects of sauropod vertebral morphology, serial position recapitulates ontogeny (Wedel and Taylor 2013b), it shouldn’t be surprising that we see differences in the prominence of the epipophyses along the neck.

Back to Qijianglong

By now it should be clear that the “finger-like processes” in Qijianglong are indeed epipophyses, and although they are quite long, they aren’t fundamentally different from what we see in many other sauropods. I haven’t gone to the trouble, but one could line up all of the vertebrae figured above in terms of epipophysis size or length, and Qijianglong would sit comfortably at one end with Omeisaurus and Mamenchisaurus, just beyond Nigersaurus and Jobaria.

Cervical vertebrae of Qijianglong (Xing et al. 2015: fig. 11)

The strangest thing about the epipophyses in Qijianglong is that they seem to be bent or broken downward in two of the vertebrae (B and H in the figure above). I assume that’s just taphonomic distortion – the cervical shown in H wouldn’t even be able to articulate with the vertebra behind it if the epipophysis really drooped down like that. The epipophyses in Qijianglong seem to mostly manifest as thin spikes of bone (or maybe plates, as shown in B and I), so it’s not surprising that they would get distorted – most of the vertebrae shown above have cervical ribs that are incomplete or missing as well.

One more noodle-y thought about big epipophyses. I wrote in the last section that I’ve never seen them in titanosaurs, possibly because titanosaurs have big neural spines for their epaxial muscles to attach to. Maybe long, overhanging epipophyses are so common in mamenchisaurids because their neural spines are so small and low. Although we tend to think of them as a basal group somewhat removed from the “big show” in sauropod evolution – the neosauropods – mamenchisaurids did a lot of weird stuff. At least in terms of their neck muscles, they may have been the most birdlike of all sauropods. Food for thought.

Harris, J. D. (2004). Confusing dinosaurs with mammals: tetrapod phylogenetics and anatomical terminology in the world of homology. The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology, 281(2), 1240-1246.

Hatcher, J.B. 1901. Diplodocus (Marsh): its osteology, taxonomy and probable habits, with a restoration of the skeleton. Memoirs of the Carnegie Museum 1:1-63 and plates I-XIII.

Hatcher, J.B. 1903. Osteology of Haplocanthosaurus with description of a new species, and remarks on the probable habits of the Sauropoda and the age and origin of the Atlantosaurus beds; additional remarks on Diplodocus. Memoirs of the Carnegie Museum 2:1-75.

Figure 4: Effect of adding cartilage to the neutral pose of the neck of Diplodocus carnegii CM 84. Images of vertebra from Hatcher (1901:plate III). At the bottom, the vertebrae are composed in a horizontal posture. Superimposed, the same vertebrae are shown inclined by the additional extension angles indicated in Table 2.

Yes, that posture is ludicrous — but the best data we currently have says that something like this would have been neutral for Diplodocus once cartilage is taken into account. (Remember of course that animals do not hold their necks in neutral posture.)

The great news here is that PeerJ moved quickly. In fact here’s how the time breaks down since I submitted the manuscript (and made it available as a preprint) on 4 November:

28 days from submission to first decision
3 days to revise and resubmit
3 days to accept
15 days to publication

TOTAL 49 days

Which of course is how it ought to be! Great work here from handling editor Chris Noto and all three reviewers: Matt Bonnan, Heinrich Mallison and Eric Snively. They all elected not to be anonymous, and all gave really useful feedback — as you can see for yourself in the published peer-review history. When editors and reviewers do a job this good, they deserve credit, and it’s great that PeerJ’s (optional) open review lets the world see what they contributed. Note that you can cite, or link to, individual reviews. The reviews themselves are now first-class objects, as they should be.

At the time of writing, my paper is top of the PeerJ home-page — presumably just because it’s the most recent published paper, but it’s a nice feeling anyway!

A little further down the front-page there’s some great stuff about limb function in ratites — a whole slew of papers.

November 5, 2014

Last night, I submitted a paper for publication — for the first time since April 2013. I’d almost forgotten what it felt like. But, because we’re living in the Shiny Digital Future, you don’t have to wait till it’s been through review and formal publication to read it. I submitted to PeerJ, and at the same time, made it available as a preprint (Taylor 2014).

It’s called “Quantifying the effect of intervertebral cartilage on neutral posture in the necks of sauropod dinosaurs”, and frankly the results are weird. Here’s a taste:

Taylor (2014:figure 3). Effect of adding cartilage to the neutral pose of the neck of Apatosauruslouisae CM 3018. Images of vertebra from Gilmore (1936:plate XXIV). At the bottom, the vertebrae are composed in a horizontal posture. Superimposed, the same vertebrae are shown inclined by the additional extension angles indicated in Table 1. If the slightly sub-horizontal osteological neutral pose of Stevens and Parrish (1999) is correct, then the cartilaginous neutral pose would be correspondingly slightly lower than depicted here, but still much closer to the elevated posture than to horizontal. (Note that the posture shown here would not have been the habitual posture in life: see discussion.)

A year back, as I was composing a blog-post about our neck-cartilage paper in PLOS ONE (Taylor and Wedel 2013c), I found myself writing down the rather trivial formula for the additional angle of extension at an intervertebral joint once the cartilage is taken into account. In that post, I finished with the promise “I guess that will have to go in a followup now”. Amazingly it’s taken me a year to get that one-pager written and submitted. (Although in the usual way of things, the manuscript ended up being 13 pages long.)

To summarise the main point of the paper: when you insert cartilage of thickness t between two vertebrae whose zygapophyses articulate at height h above the centra, the more anterior vertebra is forced upwards by t/h radians. Our best guess for how much cartilage is between the adjacent vertebrae in an Apatosaurus neck is about 10% of centrum length: the image above shows the effect of inserting that much cartilage at each joint.

And yes, it’s weird. But it’s where the data leads me, so I think it would be dishonest not to publish it.

I’ll be interested to see what the reviewers make of this. You are all of course welcome to leave comments on the preprint itself; but because this is going through conventional peer-review straight away (unlike our Barosaurus preprint), there’s no need to offer the kind of detailed and comprehensive comment that several people did with the previous one. Of course feel free if you wish, but I’m not depending on it.

References

Gilmore Charles W. 1936. Osteology of Apatosaurus, with special reference to specimens in the Carnegie Museum. Memoirs of the Carnegie Museum11:175–300 and plates XXI–XXXIV.

August 21, 2014

I have often argued that given their long hindlimbs, massive tail-bases, and posteriorly-located centers of mass, diplodocids were basically bipeds whose forelimbs happened to reach the ground. I decided to see what that might look like.

Okay, now obviously I know that there are no trackways showing sauropods actually getting around like this. It’s just a thought experiment. But given how close the center of mass of Diplodocus is to the acetabulum, I’ll bet that this pose was achievable in life. If diplodocids had just pushed the CM a few cm farther back, they might have dispensed with forelimbs entirely, or done something different with them, like re-evolved grasping hands.

Image modified from Gilmore (1932: plate 6). Here’s a horizontal-necked bipedal Diplodocus and the original pose:

July 13, 2014

Now think of this. Its neck is 8.5m long. Knock of one measly meter — for example, by removing one vertebra from the middle of the neck — and you have 7.5 m.

Supersaurus’s neck was probably TWICE that long.

Holy poo.

I replied that I was indeed freaked out, and that it had given me an idea for a post, which you are now reading. I didn’t have a Giraffatitan that was sufficiently distortion-free, so I used my old trusty Brachiosaurus. The vertebra you see there next to Mike and next to the neck of Brachiosaurus is BYU 9024, the longest vertebra that has ever been found from anything, ever.

Regarding the neck length of Supersaurus, and how BYU 9024 came to be referred to Supersaurus, here’s the relevant chunk of my dissertation (Wedel 2007: pp. 208-209):

Supersaurus is without question the longest-necked animal with preserved cervical material. Jim Jensen recovered a single cervical vertebra of Supersaurus from Dry Mesa Quarry in western Colorado. The vertebra, BYU 9024, was originally referred to “Ultrasauros”. Later, both the cervical and the holotype dorsal of “Ultrasauros” were shown to belong to a diplodocid, and they were separately referred to Supersaurus by Jensen (1987) and Curtice et al. (1996), respectively.

BYU 9024 has a centrum length of 1378 mm, and a functional length of 1203 mm (Figure 4-3). At 1400 mm, the longest vertebra of Sauroposeidon is marginally longer in total length [see this post for a visual comparison]. However, that length includes the prezygapophyses, which overhang the condyle, and which are missing from BYU 9024. The centrum length of the largest Sauroposeidon vertebra is about 1250 mm, and the functional length is 1190 mm. BYU 9024 therefore has the largest centrum length and functional length of any vertebra that has ever been discovered for any animal. Furthermore, the Supersaurus vertebra is much larger than the Sauroposeidon vertebrae in diameter, and it is a much more massive element overall.

Neck length estimates for Supersaurus vary depending on the taxon chosen for comparison and the serial position assumed for BYU 9024. The vertebra shares many similarities with Barosaurus that are not found in other diplodocines, including a proportionally long centrum, dual posterior centrodiapophyseal laminae, a low neural spine, and ventrolateral flanges that connect to the parapophyses (and thus might be considered posterior centroparapophyseal laminae, similar to those of Sauroposeidon). The neural spine of BYU 9024 is very low and only very slightly bifurcated at its apex. In these characters, it is most similar to C9 of Barosaurus. However, theproportions of the centrum of BYU 9024 are more similar to those of C14 of Barosaurus, which is the longest vertebra of the neck in AMNH 6341. BYU 9024 is 1.6 times as long as C14 of AMNH 6341 and 1.9 times as long as C9. If it was built like that of Barosaurus, the neck of Supersaurus was at least 13.7 meters (44.8 feet) long, and may have been as long as 16.2 meters (53.2 feet).

Based on new material from Wyoming, Lovelace et al. (2005 [published as Lovelace et al. 2008]) noted potential synapomorphies shared by Supersaurus and Apatosaurus. BYU 9024 does not closely resemble any of the cervical vertebrae of Apatosaurus. Instead of trying to assign its serial position based on morphology, I conservatively assume that it is the longest vertebra in the series if it is from an Apatosaurus-like neck. At 2.7 times longer than C11 of CM 3018, BYU 9024 implies an Apatosaurus-like neck about 13.3 meters
(43.6 feet) long.

Bonus comparo: BYU 9024 vs USNM 10865, the mounted Diplodocus longus at the Smithsonian, modified from Gilmore 1932 (plate 6). For this I scaled BYU 9024 against the 1.6-meter femur of this specimen.

If you’d like to gaze upon BYU 9024 without distraction, or put it into a composite of your own, here you go:

References

Gilmore, C. W. 1932. On a newly mounted skeleton of Diplodocus in the United States National Museum. Proceedings of the United States National Museum 81, 1-21.